Apparent Wind Calculator

Apparent Wind Calculator takes the maths out of one of sailing's most important concepts. Feed in your true wind angle, true wind speed, and boat speed — and instantly see your apparent wind angle and speed, visualised as a live vector diagram.

Whether passage planning, under sail or just getting your head around why the wind always seems to come from forward when you bear away, this app makes it immediately clear.

BOAT POLAR

Load a polar table and the app sets your boat speed automatically based on your true wind angle and wind speed. Built-in presets cover small, medium, and large monohulls and catamarans — or enter your own target speeds for a custom polar. With auto-fill enabled, every diagram you see reflects realistic performance numbers for your boat, not a guess.

FEATURES

• Live vector diagram showing true wind, apparent wind, and boat velocity as scaled arrows — updates in real time as you move the sliders
• Monohull and catamaran boat graphics that respond to your apparent wind angle
• Boat polar table with presets for monohulls and catamarans, fully editable
• Auto-fill boat speed from your polar for realistic results
• Point of sail readout — from Close Hauled to Deep Run
• Port and starboard tack display
• Works entirely offline, no account required

WHO IT'S FOR

Sailing students learning the theory, racers checking their VMG angles, cruisers planning passages, and coaches explaining wind shifts to crew.

The apparent wind is what your sails actually feel. This app helps you understand it.